Raw Food or Cooked Food, Which is the Healthiest? Put Down that Kale Smoothie!
Guest post by Diana Rodgers, RD, LDN, NTP. This article originally appeared in the Winter 2012 edition of The Nutritional Therapist.
I hear and read about many people making kale smoothies, consuming raw nuts,and munching salads consisting of rawbroccoli. So, I decided to take a look atsome research to see what the nutritionalcosts were of eating raw food. I found that it may better for your body to consumeprimarily cooked or lacto-fermented vegetables. Breaking down the cellular structure of vegetables through these methods greatly increases the digestibility and nutrient absorption in vegetables.
Potential Danger to Eating Raw Foods
May Lead to Thyroid Issues
Certain foods can cause disrupted thyroid hormone production.Foods belonging to the cruciferous familyare called “crucifers,” and include broccoli, kale, cauliflower, Brussels sprouts, cabbage, mustard, kohlrabi, and turnips. These foods may reduce thyroidfunction by blocking thyroid peroxidase,and by disrupting messages that aresent across the membranes of thyroidcells. Cooking these vegetables greatly reduces these negative effects.
May Cause Hormonal Regulation Issues
Cooking may also have a positiveeffect on net energy in the body. Humanson vegetarian diets exhibit higher reproductive performance when eating cookedfood than raw food. Evidence of low energy intake in women eating predominantly raw food is supported by theirhaving higher rates of amenorrhea ormenstrual irregularities than those eatingcooked food.
In one study, it was foundthat menstruation was absent in 23% offemales of childbearing age who ate atleast 70% of their food raw and in 50% ofwomen reporting a 100% raw diet. Although these women were primarily vegetarian, the addition of raw meat to thediet did not change the odds of ovariansuppression. The researchers concludedthat women suffered because of their relatively low net energy gain as a consequence of eating their food raw. Anutritional analysis suggested that in traditional communities, a diet of raw wildfoods would render survival and reproduction difficult. Learn more about the energy loss through consumption of raw food here.
May Cause Food-Borne Illness
Constant exposure to pathogens and bacteria through raw food can overcrowd the gut flora and cause food-borne illness, food poisoning, or dysbiosis. Consuming conventionally farmed raw food can increase the likelihood of being exposed to harmful bacteria like Salmonella enteritidis and Listeria monocytogenes.
May Cause Digestive Upset
Foods high in insoluble fibers like kale, cauliflower, broccoli, etc. can cause some digestive troubles as they are not absorbed by the body. Instead they call on water from your digestive system and can cause inflammation to an already inflamed gut. Research shows that masticating or cooking veggies and fruit can improve overall digestibility and energy value.
Benefits of Eating Cooked or Fermented Foods
Research suggests several reasons why cookingmight increase the energy available frommeat
It may increase food intake through positive effects on palatability related to texture and flavor
Renderproteins more digestible through denaturation
Lowers the tax on digestionthrough food softening
Reduce immune up-regulation by eliminating food-borne pathogens
Given that texturalchanges are at least partially responsiblefor the proposed positive effects of cooking on intake, digestibility, and the cost ofdigestion, non-thermal processing methods that manipulate texture, such aspounding, may likewise be effective in improving the net energy value of meat.
It is important to note that eating cooked,very lean meats has a nutritional cost. Archaeological evidence suggests that fat derived from bone marrow may havebeen preferred over muscle tissue as asource of energy and nutrients amongearly humans. Diets deriving more than50% of calories from lean protein can lead to negative energy balance, so-called‘‘rabbit starvation,’’ due to the high metabolic costs of protein digestion.
Foods have been heat-treated for manycenturies, since our ancestors learned, bytrial and error, to master fire for cookingpurposes approximately 700,000 years ago, tomodify the taste and preserve nutritionalproperties of foods. The invention andcontinuous development of food treatment has had a substantial, if not major impact on the intellectual, societal, andeconomic development of mankind.
Fermentation Improves Gut Flora
The health benefits of fermentation have been known for centuries. In 76 A.D., the Roman historian Plinio advocated the use of fermented milks for treating gastrointestinal infections. Fermentation is a non-thermal processthat produces chemical changes by enzymes produced from bacteria, microorganisms, or yeasts and is one of the oldest-known food preservation techniques.
During fermentation, the carbohydrateenergy source in food, such as lactose inmilk, is converted to lactic acid. The samehappens when pickles are produced fromcucumbers. Yeasts convert glucose to ethanol and carbon dioxide. Many health-producing secondary metabolites are produced through fermentation, especially Bvitamins and bioactive peptides whichcan be antimicrobial and immune-stimulatory.
In the early 1900s it was realized that bifidobacteria may be effective inpreventing infection in infants and theconsumption of fermented milks wereseen to reverse putrefactive effects of thegut micro flora, leading to the development of the probiotic concept. Probioticsare now used in the treatment of infections and used to promote a healthy immune system. Consuming fermented foods will improve the presence ofhealthy bacteria in the gut.
Cooking can Eliminate Toxins
One of the most important beneficialeffects of food processing is that it destroysunwanted compounds and microorganisms. Pathogenic bacteria are killed whenexposed to heat. Cooking also deactivatesanti-nutritional factors such as proteaseinhibitors and other natural toxins.
Thesecond effect is enhanced digestibility offood and bioavailability of nutrients. Forexample, gelatinization of starch makespossible its hydrolysis by amylase enzymes. Destruction of cell walls in vegetables improves the bioavailability ofcompounds such as carotenoids and polyphenols. Nuts and seeds contain many anti-nutrients in their rawstate.Soakingyour nuts overnight will increase the bio-availability of the nutrients in nuts andseeds.
Pounding, curing and cooking meat is beneficial.
When considering meat, there seems to besome evidence that processing meat either by pounding, drying, curing or cooking is beneficial. Pounding meat andmaking it soft seems to reduce the expense ondigestion, partly because it passes morequickly through the gut.
The collagen surrounding each fascicle of muscle fibersgenerally remains too tough for mastication until heated to 60–70° C, when collagen begins to be hydrolyzed into gelatin,a soluble protein. Although the muscle fibers themselves remain tough, meatcooked beyond this temperature leads to gelatinization of the collagen, which separates the muscle fibers and the gelatin.
Improved texture of meat makes it easier to chew, and easier for our bodies tobreak down. Also, when the fats areheated to oil from a fat, it’s easier for ourbile to emulsify and ultimately leads tofaster absorption. In studies, humans andchimps prefer the taste of cooked meat,leading to us eating more of it. Consumption of more protein meant larger brainsand bigger muscles as we evolved.
Cooking Kills Food-Borne Bacteria
Including strains associated with raw meatproducts such as Escherichia coli, Salmonella, Campylobacter, Staphylococcus,and Listeria. The potential energy savingsdue to reduced immune maintenance andup-regulation could be sizable. Raw wildmeat is possibly less pathogen-bearing on average than raw meatthat has been raised and processed for mass-marketconsumption.
When meat is processed at the slaughterhouse, E. coli and other pathogens from the intestines can invade theground meat. This is why most outbreaks involve burgers and other forms ofground meat but is not usually associatedwith steaks. These pathogens do not enterthe inside of the muscle tissue (steaks).
When eating industrially-raised red meat,I suggest cooking the burgers well. Slowcooking meat appears to be one of thebest methods to prepare meat for optimaldigestibility.
Lightly cooked fish is healthier than raw or fried.
In the case of fish, it appears that lightlycooked is optimal. In one study where edible portions of fresh fish were used raw,fried, cooked and undercooked, the researchers concluded that the breakdownof fish proteins were all fairly complete,but general digestibility was greatest withunderdone fish as compared to raw, fullycooked or fried fish.
In summary,
I strongly suggest cooking vegetables, consuming lacto-fermented vegetables, and other fermented foods. If you like to eat raw meat, make sure it is from a very clean source and it’s safer to stick to muscle and organs which are less likely to be contaminated with pathogens.
If you are out at a restaurant and want a standard industrially-raised beef burger, order it cooked well. Focus on slow cooking processes and using primarily grass-fed and wild meats, where the animals are much less likely to be sick (and get you sick). These meats will also have a much better ratio of omega-3 to omega-6 fats, thereby keeping inflammation down. Sashimi and other raw fish from trusted sources are ok, but lightly cooked fish seems to be optimal as far as protein digestion.
The views and opinions expressed in this post are those of the author and do not necessarily reflect the views and opinions of the NTA. They are intended for general information purposes, and are not to be considered a substitute for medical advice, diagnosis, or treatment.
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Diana Rodgers, RD, LDN, NTP is a “real food” nutritionist living on a working organic farm near Boston, Massachusetts that runs a vegetable and meat CSA. She is the author of two bestselling cookbooks and runs a clinical nutrition practice. Diana writes and speaks about the intersection of optimal human nutrition, environmental sustainability, animal welfare and social justice. She is also the producer of The Sustainable Dish Podcast, interviewing experts in the environmental and health movement. Her new film project examines the environmental, nutritional and ethical case for “better meat’. She can be found at www.sustainabledish.com.
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